Vitamins and especially carotenoids are generally insoluble in polar solvents, especially water. However, it is desirable for most applications that these compounds should be present in a soluble form in such solvents. This is of particular importance to achieve a high bioavailability of these compounds as active ingredients. It is also important in exploiting the colouring power of carotenoids which is of great interest for the colouring of foodstuffs. Therefore, the formation of cyclodextrin inclusion complexes with vitamins or carotenoids is of particular interest for conferring solubility in polar solvents.
Attempts have been made to formulate carotenoids in polar solvents. The carotenoids may be dissolved in an oil phase and/or in an organic solvent and processed with water to form an emulsion. In another process a carotenoid is ground in an oil and the resulting suspension is then emulsified in water to produce an emulsion.
These formulations have the disadvantage that they are turbid in water, since the suspension or emulsion consists of particles or light-scattering droplets. In such suspensions and emulsions the active ingredients are usually present as particles having a size of 0.1 to 10 .mu.m. Also, such suspensions or emulsions of carotenoids do not have lasting stability. Further, the carotenoids are readily decomposed by the action of heat and light.
Cyclodextrins are known to form inclusion complexes soluble in polar solvents with a large number of compounds. However, cyclodextrins have not been successfully used to make the carotenoid 62 -carotene soluble in a polar solvent.
In Japanese published Kokai 26 72 61, .beta.-carotene is mixed together with a cyclodextrin. However, solutions are not obtained. Rather, suspensions ar formed which again separate upon standing.